Piston for steam-engines



UNITED sTATEs PATENT OFFICE.

J. K. ROBIXSON AND J. M. CLARK, OF BELLAIRE, OHIO.

PISTON FOR STEAM-ENGINES.

Specification of Letters Patent No. 30,351, dated October 9, 1860.

To a-ZZ whom it may concern:

Be it known that we, JOHN K. ROBINSON and JOHN M. CLARK, both of Bellaire, in the county of Belmont and State of Ohio, have invented certain new and useful Improvement-s in Pistons for Steam -Engines, of which the followinoV is a full7 clear, and eX- act description, reference being had to the accompanying drawings, which make part of this specification, and in which- Figure l, represents a view (partly in perspective, and partly in section) of a piston embracing our improvements. Fig. 2, represents a view, in perspective, of the piston-head detached from the other parts; and F ig. 3, represents a similar view of the inner side of the follower of the piston.

Our invention relates to that class of pistons for steam engines in which the pressure of the steam itself is caused to expand the packing-rings thereof; and our improvements consist, first, in constructing the bolts which hold the piston-head and follower together with valve-seats in their small ends, so that they shall serve the double purpose of holding the plates together, and of constituting an adjustable seat for the ballvalve; secondly, in providing a flange or rim around both piston-head and follower, in combination with a key across the pistonhead (on its upper side and between the flanges in horizontal engines) to support the packing-ring, whereby the ring is at all times held rmly in a central position relative to .the piston and the steam allowed to circulate beneath the ring entirely around the piston-head. To accomplish these results we take a solid piston-head and drill a series of holes or channels entirely through it at a suitable distance from its periphery and parallel or nearly so to the piston-rod. Another series of holes are bored into the head about midway between the flanges,v at right angles to, and communicating with the channels above mentioned. rFliese holes admit the steam from the cylinder' to the under side of the packing-rings. A suitable valve is arranged in each channel just at its point of intersection with the steam-opening which leads to the ring, in such manner that while alternately cutting off the steam from each side of the piston-head, the communication with the steam-opening is always kept open,

I and the pressure upon the packing-ring constantly maintained.

The bolts which secure the follower to the head may be perforated and form a part of each channel; which arrangement likewise affords great facilities for regulating the play of the valves and the consequent amount of steam-pressure upon the rings.

Shoulders or flanges may be turned upon the head and follower for the purpose of maintaining the ring in its proper relative position. In a horizontal cylinder the bottoni of the packing-ring wears more rapidly than any other part, and this wearing tends to throw the ring out of its true position. As a further preventative of this displacement, in addition to the rims on the head and follower we sometimes employ a key or wedge which fits in a slot running longitudinally across the piston-head, the thickness of which wedge may be varied as circumstances may require.

The accompanying drawings representa convenient arrangement of parts for carrying out t-he objects of our invention. The piston-head (B) is secured to the piston-rod (A) by means of a nut (a) in the usual manner. The main body (B) of the head is turned down to a diameter somewhatless than that of the packing-ring (D) which slips loosely on this reduced part. The follower (C) fits on a shoulder (o2) turned on the head (B). Both the head and follower are provided with rims (ZJ and c) on which the packing-ring fits, and by which it is prevented from wabbling. A key (b1) inserted into a slot in the head also serves as an additional support to the ring. We prefer to use one ring only, although more than one may be used if deemed expedient.

The head and follower are united by bolts (E) which in this instance are tapped into the head. These bolts and the head are perforated longitudinally so as to form channels (f, f2) for the passage of the steam. Ports (f1) are also formed in the head, at right angles to, and communicating with the channels (f, f2). A valve-chamber is formed in the head at the intersection of each port (f1) with its channels (f, f2) and in this chamber a. ball-valve (F) plays. The size of this chamber, and the consequent amount of play allowed the valve is regulated by means of a washer (e) on the bolt (E) the thickness of which Washer may be varied at will. The details of the above described arrangements are clearly shown in the sectional part of Fig. 1, of the drawings.

The operation of the piston is as follows: The head being secured on the rod as de-` scribed with the key (b1) on its upper side, the ring (D) `is slipped on over the rim (b) and key (b1). The edges of the ring and the flanges (B, O) of the head and follower are ground steam-tight to prevent leakage. Any escape of steam at the joint of the ring is prevented by means of a guard-plate of a construction similar to that secured to us by Letters Patent of the United States dated Aug. 14, 1860. A portion of each rim (b, c) is removed to leave a Vacancy into which this guard plate may fit and prevent any tend-r enc of the ring to turn in its bearings. The follower (O) is now placed on the shoulder (b2), its rim (c) fitting between the packing-ring and the reduced portion of the head The balls being placed in their respective valve-chambers, the head and follower are then securely fastened together by the bolts The cylinder-head may then be put on, and steam admitted to the cylinder. As the piston moves backward the balls (F) are forced against the piston-head (B) and close the channels (f2) (as shown in Fig. l). TheY steam then rushes through the channels (f) and Xprints (f1) and expands the packing-ring. en the motion of the piston is reversed, the balls close the channels (f) and open the opposite ones (f2), through which the steam rushes as before, this process being repeated at each stroke of the piston. The range of motion of the ball, and consequently, the steampressure upon the ring may be regulated by varying the thickness of the washer (c), and the consequent depth to which the bolt enters the head. n

,/Vhat we claim as our invention and desire to secure by Letters Patent, is

1. The valve-seat bolts constructed substantially in the manner and for the double purpose herein described.

2. The combination of the key (b1) with the rims c) on the piston-head and follower, substantially in the manner and for the purpose described.

In testimony whereof we have hereunto subscribed our names.

JOHN K. ROBINSON. JOHN M. CLARK;

Witnesses:

J oHN KELLY, JN0. J. POWELL. 

